I apologize in advance, I'm very new to programming in general, especially C++, and I'm trying to update inherited code as best I can so please bear with me.

I have a main dialog which has (DDX?) controls for the user. eg a slider, and a combo box.
Previously, an image adjusted by these controls was in the same dialog.
I need to put this image in a New, separate dialog but it still must be controlled by the slider and combo box on the main dialog.
(I hope that makes sense)

My question is how can I pass the control's variables between the dialogs? I have, say,
DDX_Control(pDX, IDC_ComboBrightness, m_Brightness
I was told that I could do something like:
	ImageDlg(CWnd* pParent = NULL, CComboBox m_Brightness);  // standard constructor
But I get errors including: Missing default parameter for parameter 2

I also need to pass the image array, is that perhaps the same method?

Even if someone could even point me to an appropriate MSDN article or a tutorial, I'm happy to do the reading - I just can't seem to hit on the right search parameters, or my C++ to English translations aren't as good as they should be yet.

Thanks so much!